Drill bit

ABSTRACT

A drill bit having a shank provided with portions of different cross-sectional configuration to enable use of the bit in conventional chucks having either two, three or more jaws.

United States Patent Inventor Willis S. Fenli [56] References CitedLivonia UNITED STATES PATENTS $5 if 1969 1209.362 12/1916 Turner 77/71 7Paemed J 1971 3,136,347 6/1964 Lmquist 145/11 Assignee 'I'RW Inc.Primary ExaminerRobert C. Riordon Cleveland, Ohio AssistantExaminer-Michael Koczo, Jr.

AttameyWhittemore, Hulbert & Belknap DRILL BIT 2 Claims,9 Drawing Figs.

U.S. Cl..... 408/226 Int; Cl ..B27g 15/00,

1323b 5 1/02 ABSTRACT: A drill bit having a shank provided with portionsField of Search 145/ 1 16, of different cross-sectional configuration toenable use of the bit 287/126; 279/56, 48, 69, 89

in conventional chucks having either two, three or more aws.

DRILL BIT c Conventional hand braces are generally provided with chuckshaving two jaws which requires that drill bits to be used therein beprovided with a shank portion having a specific configuration enablingit to be securely gripped by the jaws of the chuck. Customarily drillbits for use with the conventional two-jaw chuck in a hand brace havebeen provided with a shank having its outer end of tapered squareconfiguration. The chucks used in power drills are usually provided withchucks having three jaws which are not adapted to receive and grip adrill bit shank designed to be used with a two-jaw chuck. It hastherefore been customary to manufacture two or more different types ofdrill bits, each of which is specifically adapted for use with only onetype of chuck.

It has been proposed to manufacture drill bits having both round andsquare cross-sectional areas, as in U.S. Pat. No. 2,029,447, but theconstruction disclosed in such patent has the obvious disadvantage ofrequiring the user to cut off a portion of the shank at a selected pointdetermined by the type of chuck in which the bit is to be used. This hasthe further disadvantage of eliminating any possibility of subsequentlyusing the bit in a different type of chuck. It has also been proposed inU.S. Pat. No. 3,l36,347 to provide a shank having areas of differentcross-sectional shapes to adapt the same for different types of chuckswithout cutting off any part of the shank. However, the constructiondisclosed in the last-mentioned patent requires the use of a speciallydesigned chuck when the shank is to be gripped on the round portionthereof.

The present invention provides a shank for a drill bit which is formedso as to adapt the same for use with chucks having two, three or morejaws, and accordingly the shank is provided with a round portion at itsouter end and is provided with a generally square portion inwardly fromthe outer end so that the square portion of the shank may be gripped ina conventional two-jaw chuck while the round portion is'adapted to begripped by the jaws of a conventional three-jaw chuck. The dimensions ofthe square portion of the shank relative to the diameter of the roundportion thereof are such that the bit may be used interchangeably in twoor three jaw chucks without interference and without the necessity ofcutting off any part of the shank, thereby enabling the same to. be usedwith any conventional chuck throughout the life of the drill bit.

In the drawings:

FIG. I is an elevational view of a drill bit according to the presentinvention;

FIG. 2 is a fragmentary perspective view of the shank of the drill bitshown in FIG. 1;

FIG. 3 is an elevational view of a modified form of the invention;

FIG. 4 is a fragmentary sectional view of the drill bit shown in FIG. 1,showing the same in use in a conventional two-jaw chuck;

FIG. Sis a sectional view taken on line 5-5 of FIG. 4;

FIG. 6 is a fragmentary sectional view showing the drill bit shown inFIG. 3 gripped by the chuck shown in FIG. 4;

FIG. 7 is a sectional view taken on line 7-7 of FIG. 6;

FIG. 8 is a fragmentary sectional view of the drill bit used with aconventional three-jaw chuck; and

FIG. 9 is a sectional view taken on line 9-9 of FIG. 8.

In FIGS. 1 and 2 there is illustrated a drill bit 10 having a flutedportion 12 and a shank 14 having a portion 16 at its outer end which isof round cross section. The shank is provided with a generally squareportion 18 inwardly along the shank from the round portion 16. Thesquare portion 18 comprises four flats 20 with the dimension across apair of opposed flats 20 being less than the diameter of the roundportion 16 to define outwardly facing shoulders 22. The flats 20 aredimensioned so that they do not intersect in sharp corners but terminatein the surface of the shank to define narrow bands 24 which separate theadjacent flat surfaces 20. The bands 24 conform to the surface of theround portion 16 of the shank.

The dimension across the flats of the square portion 18, while less thanthe diameter of the round portion 16, is preferably only slightlygreater than the largest dimension which would result in theintersection of the flats in sharp corners, thereby to provide flatshaving sufficient area for adequate gripping by the jaws of the chuckand defining shoulders 22 of substantial depth for a purpose to bedescribed.

The shank 14 may also be provided with a similar square portion 26 atits outer end with the sides thereof parallel to the sides of the flats20 of the square portion 18 and of the same dimensions. The drill bit 10is shown in FIG. 4 inserted into a conventional two-jaw chuck whichcontains a pair of jaws 30 adapted to receive the end of the shanktherebetween and which are cammed inwardly into'gripping engagement withthe shank by a tapered cam member 32 when the sleeve 34 is threadedinwardly on the drive shaft 36. A spring member 38 tends to urge theinner ends of the jaws 30 toward each other.

When used with a two jaw chuck of the type described, the shank isinserted until the flats 20 are in position for engagement by thelowerends or gripping portions 40 of the jaws 30. The jaws 30 areprovided with V-shaped grooves 42, the sides of which are perpendicular,and which are adapted to receive opposite corners of the square portionI8. The V-shaped grooves 42 extend along the entire length of the jaws,but inwardly of the gripping portions 40 thereof such grooves arerecessed outwardly and taper upwardly along the length of the jaws. Thesides of the grooves 42 in the end portions 40 of the jaws do not alwaysintersect in sharp comers and the dimensions of the flats 20 asdescribed above therefore provide faceto-face engagement of the jawswith the flats 20. The square portion 26 at the outer end of the shankis also adapted to seat within the grooves at the upper end of the jawsto provide a secure gripping of the jaws at spaced points along theshank 14. The provision of the squared portion 26 at the outer end ofthe shank is not necessary to provide adequate gripping of the shank ina two-jaw chuck, particularly in smaller size drill bits such as thatshown in FIG. 3, but the additional squared portion may be desirable inlarger size drills, not only to provide a second gripping surface, butalso to eliminate any possible interference between the end of the shankand the inner portions of the jaws in some types of chucks.

With the shank gripped as shown in FIG. 4, the portions 40 of the jawswill engage behind the shoulders 22 defined by the flats 20 to preventaccidental withdrawal of the bit from the chuck.

FIG. 3 illustrates a drill bit 50 of smaller size than the bit 10 andhaving a shank 52 provided with a round portion 54 at its outer end anda square portion 56 having the same shape as the squared portion 18 ofthe drill bit 10. FIG. 6 illustrates the gripping of the drill bit 50 ina two-jaw chuck of the kind described above. In this form of theinvention the gripping of the square portion 56 is the same as describedin reference to FIG. 4, while the round outer end of the shank seats inthe grooves 42 in the manner shown in FIG. 7 to grip the shank ataxially spaced points thereby stabilizing the bit.

FIG. 8 illustrates use of the drill bit 10 in a three-jaw chuck havingthree equally spaced jaws 60 which are adapted to grip the round portion16 of the shank without interference from the square portion 18 or 26.The entire length of the shank 14 may be of the same round cross sectionso that the jaws 60 may grip the round portion 16 above the squareportion 18 or both above and below the square portion 18, as shown inFIG. 8.

The present invention provides a drill bit of inexpensive constructionwhich adapts the same for either two or three jaw chucks or even fourjaw chucks without the necessity of the user cutting off or otherwisemodifying any part of the shank. The shank construction described hasbeen found to be capable of use with all types of conventional two jawchucks as well as three jaw chucks.

What I claim as my invention is:

l. A drill bit for use in either two three-jaw three jaw chucks, havinga shank portion of round cross section adgripped by a conventionaltwo-jaw chuck with the jaws thereof engaging said flats and saidshoulder to prevent accidental withdrawal of said bit.

2. A drill bit accordingto claim 1 wherein said shank is provided with asecond generally square portion at its outer end, said second squareportion having substantially the same dimensions as the first-mentionedsquare portion and also adapted to be gripped by the jaws in a two-jawchuck.

1. A drill bit for use in either two three-jaw three jaw chucks, havinga shank portion of round cross section adjacent its outer end, and agenerally square portion disposed inwardly along the shank from saidround portion, the dimension across the flats of said square portionbeing less than the diameter of said round portion to define a shoulderfacing toward the drill end of said bit, said dimension being such thatadjacent flats do not meet in sharp corners but are separated by anarrow band of said round portion, said round portion being adapted tobe gripped by the jaws of a conventional three-jaw chuck, said squareportion being adapted to be gripped by a conventional two-jaw chuck withthe jaws thereof engaging said flats and said shoulder to preventaccidental withdrawal of said bit.
 2. A drill bit according to claim 1wherein said shank is provided with a second generally square portion atits outer end, said second square portion having substantially the samedimensions as the first-mentioned square portion and also adapted to begripped by the jaws in a two-jaw chuck.